ACKNOWLEDGEMENTS 



For their kind permission to reproduce paintings and photo- 

 graphs in this book, the Author wishes to thank the following : 



The National Portrait Gallery, for Michael Faraday and 

 Edward Jenner. 



The Royal Society, for Sir F. Gowland Hopkins. 



The Director of the Pasteur Institute, Paris, for Louis 



Pasteur. 



Messrs. Macmillan and Co., Ltd., for Thomas Huxley (from 

 Memoirs of Thomas Huxley, by M. Foster). 



Messrs. Allen and Unwin, Ltd., for Gregor Mendel (from 

 Life of Mendel, by Hugo litis). 



Picture Post, for Claude Bernard. 



Harper's Magazine, for Charles Darwin. 



Martha Marquardt, for Paul Ehrlich (from her Paul Ehrlich, 

 published by Heinemann). 



The editor. The Journal of Pathology, for Theobald Smith. 



Mrs. W. B. Cannon, for Walter B. Cannon. 



Messrs. J. Russell and Sons, for Sir Henry Dale and Sir 

 Howard Florey. 



Topical Press, for Sir Alexander Fleming. 



Lotte Meitner-Graf, for Max Planck. 



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